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Introduction

Using ultrasound for needle guidance has become standard practice in many regional anesthesia procedures. The out-of-plane approach may be preferred in some circumstances due to anatomical obstructions, steep angle requirements or challenges with the size/geometry of the ultrasound probe itself. However, this approach comes with its own set of challenges due to lack of needle visibility and an increased risk of inadvertent puncture into surrounding structures. We examined a new alternative needle guide design that has a retracting stop to prevent unwanted needle advancement while allowing the user to have precise control and large depths of insertion. We hypothesized that the use of this new out-of-plane retracting stop needle guide will allow novice users to reach a predetermined target more rapidly and accurately than when compared to both the free hand out-of-plane short

Materials and Methods

After receiving IRB approval through Oregon Health and Science University we performed a randomized, non-blinded, crossover study using six medical students with no or minimal previous ultrasound experience. This study was conducted in the VirtuOHSU Lab.

Participants were oriented to the ultrasound machine and instructed on all three approaches before attempts were made. There were four separate targets placed at varying depths in the paraspinal tissue of a porcine vertebral slab. Each participant was assigned one target site to complete all three techniques. The participants were randomized to begin with the traditional out-of plane ultrasound technique or the out-of-plane needle guide and then crossed over to use the alternate techniques. The total time it took to achieve final needle position placement was measured at three separate intervals. Proximity to target was then measured by an experienced ultrasonographer utilizing the built-in on screen calipers.

We tested the significance of observed values of proximity and total procedure time using a single-factor analysis of variance (ANOVA).

Results

The mean total time spent for the needle guide group was significantly less than the other two techniques

NG 34.35secs

IP-Long 119.72secs

OP-Short 113.09secs

p= 0.021

Needle proximity was on average more accurate with the needle guide although this was not statistically significant

NG 8mm

IP-Long 15mm

OP-Short 14mm

p= 0.28

Conclusion

We successfully fabricated and validated a retreating stop needle guide. Even with relatively primitive fabrication techniques we observed a reasonable degree of accuracy in this style of guide

We observed a statistically significant reduction in total procedure times with the retreating stop needle guide, consistent with that observed with other styles of needle guide.

We did not observe any reduction in accuracy, and in fact noted a trend towards increased accuracy when used by subjects with limited experience in ultrasound although not statistically significant.